After re installation, I needed to top up the coolant ( due to losing some during removal I guess) and then drove it for the moment of truth......gutted, still drove as if it was in limp mode and no boost.

As a last ditch attempt before conceding, I swapped out the inlet pipe with the one from our ML,....the car was back!! Drove amazingly well, perhaps even better than before (placebo effect of a clean EGR

), the scan showed zero faults incl any EGR related ones.
I concluded that the new MAF sensor being the culprit must have been faulty!
It was removed sharpish, returned to Germany and a used OEM one purchased. Fitted it upon arrival and have had zero issues since and although I removed the EGR valve unnecessarily (it transpired) at least it got a clean!